Who is, equivalent to seeing He is. Beginning, with reference to the Church; not the beginning of the Church, but of the new life which subsists in the body - the Church.

The first-born from the dead (πρωτότοκος ἐκ τῶν νεκρῶν)

Defining how Christ is the beginning of the new spiritual life: by His resurrection. Compare 1 Corinthians 15:20, 1 Corinthians 15:23, and Prince of life, Acts 3:15 (note) See on Revelation 1:5, where the phrase is slightly different, "first-born of the dead." He comes forth from among the dead as the first-born issues from the womb. Compare Acts 2:4, "having loosed the pains of death," where the Greek is ὠδῖνας birth-throes. There is a parallelism between first-born of the creation and first-born from the dead as regards the relation of headship in which Christ stands to creation and to the Church alike; but the parallelism is not complete. "He is the first-born from the dead as having been Himself one of the dead. He is not the first-born of all creation as being himself created" (Dwight).

In all things

The universe and the Church.

Might have the preeminence (γένηται πρωτεύων)

Lit., might become being first. Πρωτεύω to be first only here in the New Testament. Γένηται become states a relation into which Christ came in the course of time: ἐστιν is (the first-born of all creation) states a relation of Christ's absolute being. He became head of the Church through His incarnation and passion, as He is head of the universe in virtue of His absolute and eternal being. Compare Philippians 2:6, "being (ὑπάρχων) in the form of God - was made (γενόμενος) obedient unto death." This sense is lost in the rendering might have the preeminence.